Pumping chamber decompression



y 1969 H. E. FISCHER ETAL 3,

PUMPING CHAMBER DECOMPRESSION 2 Sheets-Sheet 1 Filed March 20, 1967 "III I I M8 TR mfi mm I E mm 0 mm W m m y 1969 H. E. FlSCHER ETAL 3,457,873

PUMPING CHAMBER DECOMPRESSION 2 Sheets-Sheet 2 Filed March 20. 1967 AROLD R WARD N OE INVENTOR.

HOYARD E. FISCHER & B7 A United States Patent 3,457,873 PUMPING CHAMBER DECOMPRESSION Howard E. Fischer, Detroit, and Harold R. Ward, Pontiac, Mich., assignors to Sperry Rand Corporation, Troy, Mich., a corporation of Delaware Filed Mar. 20, 1967, Ser. No. 624,465 Int. Cl. F04b 1/02 US. Cl. 103--162 2 Claims ABSTRACT OF THE DISCLOSURE A fluid pressure energy translating device having a high pressure port and a low pressure port separated by a barrier and having a pumping chamber which communicates first with the high pressure port; then is isolated from the high and low pressure ports by the barrier and then communicates with the low pressure port. The pumping chamber being connected to low pressure momentarily while isolated from both ports to decompress'the high pressure fluid trapped in the pumping chamber resulting from its prior communication with the high pressure port.

BACKGROUND OF THE INVENTION This invention pertains to power transmission and is particularly applicable to fluid pressure energy translating devices and specifically to those of the type commonly referred to in the art as hydraulic piston pumps. More specifically, this invention pertains to a unique pump construction of decompressing the pumping chamber prior to its communication with the low pressure inlet port while the pumping chamber moves from the high pressure port to the low pressure port. Pumps of this general classification, when operated at an atmospheric inlet pressureization condition, are subject to what may be termed flow saturation. That is, as pump speed increases the fluid flow rate from the pump increases proportionately until a predetermined speed is reached at which the rate of increase in fluid flow begins decreasing rapidly, even though pump speed continues increasing. Flow saturation occurs as a result of inadequate filling of the pumping chamber with inlet fluid and consequently results in a proportionate reduction in output fluid flow. For instance, as each pumping chamber moves from the high pressure outlet port to the low pressure inlet port, it passes through a region wherein the pumping chamber is isolated from both ports. While in this region, the fluid within this pumping chamber remains at a pressure level substantially equal to the outlet fluid pressure. When the pumping chamber first communicates with the low pressure fluid within the pumping chamber surges into the inlet port creating considerable turbulence within the pumping chamber surges into the inlet port creating considerable turbulence within the inlet port cavity. This turbulence disrupts the incoming flow of inlet fluid and thus prevents adequate filling of the inlet port and pumping chamber. At low pump speeds this eflect is practically unnoticeable because the time interval during which the pumping chamber is in communication with the inlet port is such that the turbulence within the inlet cavity is dissipated and adequate filling of the inlet port and pumping chamber is substantially achieved. However, as pump speed increases, this time interval proportionately decreases and eventually reaches a critical point at which this turbulence prevents adequate filling of the pumping chamber, thus producing the characteristic referred to as flow saturation. This characteristics is further exaggerated when the outlet fluid pressure is increased. Decompression of the pumping chamber prior to communication with the inlet port substantially alleviates this problem and permits higher pump speed operation.

The prior art discloses pump construction of various types which decompresses the pumping chamber. One such method is the use of a V-shaped metering groove starting at the entrance to the inlet port, which gradually enlarges in cross-sectional area as it approaches the inlet port. This allows fluid trapped in the pumping chamber to be slowly metered from the pumping chamber into the inlet port, thus gradually decompressing the pumping chamber prior to its communication with the inlet port. Another method, as shown in P.N. 2,619,041 issued to E. H. Born, discloses a passage in the valve block which extends from the valving surface of the valve plate in the region of the barrier separating the high and low pressure ports to the inlet port. Thus, as the pumping chamber moves across the barrier in the region of the passage, the pumping chamber is decompressed by allowing fluid to flow through the passages into the inlet port. These methods, however, fail to alleviate the problem of flow saturation, in that the fluid used to decompress the pumping chamber still flows into the inlet port causing turbulence and thus disrupting the flow of inlet fluid to the pumping chamber. Another method which is used primarily on radial piston type units, as disclosed in P.N. 2,075,017 issued to E. Benedek, employs a fixed volume cavity between the high and low pressure ports which functions as an accumulator for providing predetermined, precompression pre-expansion of the pumping chamber between the exhaust and intake strokes. This method does not sufiiciently decompress the pumping chamber prior to communication with the inlet port and consequently the same basic problem results.

An object of this invention is to increase the speed range of a fluid pump operating at elevated discharge pressures to approximate the speed range of a fluid pump operating at reduced discharge pressures without experiencing a substantial loss in its volumetric eificiency when operated with low inlet pressurization.

Another object of this invention is to provide a fluid pump with simple means for decompressing the pumping chamber as it moves from the high pressure port to the low pressure port.

A further object of this invention is to precisely control the period of decompression while the pumping chamber is out of communication with the high and low pressure ports.

Another object of this invention is to provide a fluid pump with passage means which communicates with the pumping chamber as the pumping chamber moves between the high and low pressure ports and simple valving means which normally closes the passage means but which momentarily opens the passage means to connect the pumping chamber to a low pressure region disassociated from the low pressure port.

A further object of this invention is to arrange the passage means with a spaced relationship with respect to the high and low pressure ports and arrange the valving means with a spaced relationship with respect to the pumping chamber such that the distance between the high and low pressure ports may be minimal.

In the drawings:

FIG. 1 is a longitudinal transverse sectional view of a device embodying the present invention.

FIG. 2 is a view taken along the line 22 in FIG. 1.

FIG. 3 is a view taken along line 33 in FIG. 1.

FIGS. 4 and 5 are fragmentary views of FIG. 2.

Referring now 'to FIG. 1, the embodiment of the invention selected for illustration comprises a fluid pressure energy translating device 10 having a housing 12 and a valve block 14 secured thereto by mounting bolts 16. The dowel 18 maintains proper angular alignment between the valve block 14 and the housing 12. The valve block 14 has a valving surface 20 having arcuate shaped high and low pressure ports 22 and 24 illustrated in FIG. 2. The portions of the valving surface between these ports constitute barriers 25 and 27. High pressure port 22 and low pressure port 24 are individually connected by suitable passages, not shown, for fluid communication to external outlet and inlet ports 26 and 28, respectively.

The housing 12 has a longitudinal bore 30 providing a case chamber 32 containing a rotatable cylinder block 34 positioned therein. A case drain port 33 is provided for the removal of fluid from case chamber 32 which may accumulate during the operation of the device 10. Drain port 33 may be connected by suitable conduit means to a reservoir, not shown. Cylinder block 34 has a plurality of cylinders 36 in which pistons 38 are fitted for reciprocal motion to form pumping chambers 39. The pistons 38 have spherical ends 40 on which are swaged socketed shoes 42. The cylinder block 34 is positioned axially between the valve block 14 and a thrust plate 46 which, in turn, is mounted on a cylindrical thrust block 45 having an inclined surface 47 and attached there to by means not shown. Thrust block 45 is secured to shoulder 49 forming the bottom of bore 30 by means not shown. The shoes have outwardly extending flanges 48 which are contacted by an angular cage 50 provided with holes 52 corresponding to each piston 38. The cage 50 has a truncated conical bore 58 which contracts a spherical outer surface 60 of a collar 62 which is provided with a female spline 63 to engage a male spline 64 on a drive shaft 66.

A spring 68 is positioned in a central recess 70 in cylinder block 34. One end of spring 68 acts against a washer 72 and a snap ring 74 in cylinder block 34. The other end of spring 68 is exerted against a washer 76 which abuts a plurality of push rods 78 extending axially through holes 80 in cylinder block 34 into engagement with collar 62. The force exerted by spring 68 thus brings the valving face 82 of cylinder block 34 into engagement with face 20 of valve plate 14 and also biases the shoes 42 into engagement with the face 84 of thrust plate 46.

Drive shaft 66 is supported between bearings 86 and 88 and is effective to transmit torque from a prime mover, not shown, to the cylinder block 34 having a female spline 90 which engages the male spline 64, thus forming a driving connection at 92. A conventional shaft seal is provided at 94.

Each cylinder 36 has a cylinder port 96 as shown in FIGS. 1 and 3. Referring to FIG. 3, a plurality of Kingsbury pads 98, radially disposed at the outer edge of the cylinder block valving face 82, are formed by a plurality of radial recesses or slots 100 and a circular groove 102. Slots 100 are centrally located with respect to each cylinder port 96 and between each adjacent cylinder port. For instance, the slots 100 designated A, B, and C are centrally located with respect to the cylinder ports 96 designated X, Y, and Z; and slots 100* designated D and E are centrally located between cylinder ports 96 designated X and Y, and Y and Z, respectively. For convenience of explanation, the Kingsbury pads 98 adjacent slot B are designated DB and BE. A passage 104 is formed in valve block 14 by an entrance passage 106 perpendicular to the valving surface 20 and an exit passage 108 inclined to the valving surface 20. Passage 106, as shown in FIG. 2, is located in the valving surface barrier 25 at a point midway between the high and low pressure ports 22 and 24. Passage 108 is located radially outwardly of passage 106 and extends from the valving surface 20 in the region where the Kingsbury pads 98 contact the valving surface 20. The width of the slots 100 is substantially the same as the diameter of the exit passage 108.

Referring to FIG. 2, a portion of cylinder block valving face 82, illustrated by the dotted lines, is superimposed upon the valve block valving surface 20 to show the relative relationship of the cylinder ports 96, the Kingsbury pads 98 and the slots with respect to the high and low pressure ports 22 and 24 and the entrance and exit passages 106 and 108. FIG. 4 and FIG. 5 are fragmentary portions of FIG. 2 illustrating the position of the cylinder block 34 rotated slightly clockwise and counterclockwise, respectively, from that illustrated in FIG. 2.

In operation, considering the device disclosed to be used as a fixed displacement pump, the external outlet port 26 is connected to a suitable load device such as a fluid motor, not shown, and external inlet port 28 is connected to a reservoir at atmospheric pressure, not shown. Thus the fluid supplied to the external inlet port 28 is substantially at atmospheric pressure. Rotation of shaft 66 drives cylinder block 34 relatively to the stationary valve block 14. Referring to FIG. 2 with the shaft 66 and cylinder block 34 being rotated in a counterclockwise direction, fluid enters the external port 28 and flows to port 24. As the cylinders 36 circumscribes the arc corresponding to port 24, the pistons 38 move away from the valve block 14 allowing fluid from port 24 to fill the pumping chamber 39. This is commonly referred to as the inlet or suction stroke of the pump. Conversely, as the cylinders 36 circumscribes the arc corresponding to port 22, pistons 38 move toward the valve block 14 forcing fluid out of the pumping chamber 39 through port 22 to external port 26. This is commonly referred to as the outlet or exhaust stroke of the pump. The outlet fluid pressure, of course, depends upon the requirement posed by the load device connected to the external outlet port 26, and may be in the magnitude of 3000 psi.

As each cylinder port 96 moves out of communication with the high presusre port 22 toward the low pressure port 24 across the barrier 25, the fluid remaining within the pumping chamber 39 remains at substantially outlet pressure. Ordinarily, this fluid would be discharged into the low pressure port 24 when the pumping chamber 39 initially communicates with the low pressure port at a relatively high velocity thus causing considerable turbulence within the low pressure port. This turbulence is especially undesirable when the pressure of the fluid supplied to the external inlet port 28 is approximately 14.7 psi. or substantially atmospheric pressure, in that this turbulence obstructs the flow of inlet fluid into port 24 and consequently prevents proper filling of the pumping chamber 39. This results in a noticeable decrease in the volumetric efficiency of the pump when operated at high speeds.

This undesirable result is alleviated by decompressing the pumping chamber 39 prior to its communication with the low pressure port 24 through passage 104 to cavity 32. However, to maintain a high volumetric efliciency of the pump while decompressing the pumping chamber 39, direct communication between the high pressure port 22 or the low pressure port 24 and cavity 32 must be prevented and the period of decompression should be minimal.

As the drive shaft 66 drives the cylinder block 34 in a counterclockwise direction, each cylinder port 96, successively, moves from the high pressure port 22 across the barrier 25 to the low pressure inlet port 24.

Referring now to FIG. 4, which illustrates the position of the cylinder block just prior to decompression of the pumping chamber 39. Cylinder port Y first communicates with entrance passage 106 while still in communication with high pressure port 22. Kingsbury pad BE, however, blocks exit passage 108, thus preventing direct communication between the high pressure port 22 and cavity 32. When cylinder port Y rotates to the position shown in FIG. 4 an intermediate condition exists for an instant when the cylinder port is out of communication with port 22 and Kingsbury pad BE still blocks exit passage 108. As the cylinder port Y continues moving, the edge of Kingsbury pad BE forming one side of slot B gradually uncovers exit passage 108 communicating cylinder port Y with cavity 32. When the cylinder block 34 rotates to the position shown in FIG. 2, slot B fully uncovers the exit passage 108. As the cylinder port Y continues moving the edge of Kingsbury pad DB, forming the other side of slot B, gradually blocks exit passage 108. When the cylinder block 34 rotates to the position shown in FIG. 5, the exit passage is completely covered by the Kingsbury pad DB, thus preventing further communication between cylinder port Y and cavity 32. At this point cylinder port Y is not yet in communication with the low pressure port 24. As the cylinder block 34 continues to rotate, cylinder port Y communicates with the inlet port 24 while remaining in communication with entrance passage 106. However, communication between inlet port 24 and cavity 32 is prevented by Kingsbury pad DB blocking exit passage 108.

While the cylinder block rotates from the position illustrated in FIG. 4 to that position illustrated in FIG. 5, the fluid pressure within pumping chamber 39 is decompressed to a value substantially equal to the fluid pressure within cavity 32, which in turn is substantially equal to the atmospheric pressure of fluid in the reservoir.

After the pump chamber has been decompressed, the pressure of the fluid in the pumping chamber 39 and in the low pressure inlet port 24 are substantially equal. Thus, as the cylinder port 96 continues to rotate and communicates with the low pressure port 24 there is no sudden surge of fluid flow from the pumping chamber 39 to the low pressure port 24 to cause turbulence, thereby allowing proper filling of the pumping chamber during the suction stroke and increased flow capability at increased operating speed of the pump. The preceding explanation of the invention applies equally for either direction of rotation of the drive shaft 66.

Although the description of the invention contained herein pertains to a fixed displacement pump, the invention is equally applicable to a variable displacement pump. Also, by employing another passage identical to passage 104 but diametrically opposed to that shown, the invention herein disclosed is made applicable to a variable displacement pump in which the thrust plate 46 is rotatable to inclined positions on opposite sides of a center position for alternating the inlet and outlet port.

It will thus be seen that the invention herein disclosed provides a unique means for improving the speed and flow capability of a fluid pressure energy translating device when operated at elevated outlet pressures and at a depressed or atmospheric inlet pressurization to approximate the speed range and flow capability of a device operating at a low discharge pressure without a substantial loss in volumetric efficiency by decompressing the pumping chamber while it is out of communication with the high and low pressure ports.

It will further be seen that this invention provides a unique means of decompressing the pumping chamber so as to not appreciably eflect the volumetric efliciency of the device by precisely controlling the decompression period. More specifically, it will be seen that this invention concerns the use of a passage which communicates with the pumping chamber of the device as the pumping chamber moves from the high to low pressure ports and valving Cit means comprising the Kinsbury pads and slots therebetween to momentarily open the passage to thereby relieve the fluid pressure within the pumping chamber when the pumping chamber is out of communication with the high and low pressure ports, by providing a fluid flow path between the pumping chamber and the interior of the device.

What is claimed is as follows:

1. In a fluid pressure energy translating device comprising a stationary valve member having a valving surface with high and low pressure ports separated by a barrier, a rotary cylinder barrel having a valve face juxtaposed against said valving surface, said barrel having a plurality of radially disposed cyclically contracting and expanding pumping chambers exposed to said face and movable relative to said valve member such that each chamber successively communicates first with said high pressure port, then isolated from both of said ports by said barrier, and then communicates with said low pressure port, that improvement comprising: passage means having an entrance and an exit, said entrance of said passageway means being located in said barrier in said valve surface midway between said high and said low pressure ports, said chamber communicating with said entrance before said chamber moves out of communication with said high pressure port and remaining in communication with said entrance until after said chamber communicates with said low pressure port, and a plurality of Kingsbury pads arranged on said valving surface of said barrel and slots separating said pads, said Kingsbury pads and slots being disposed radially from said chamber, said slots between said Kingsbury pads being centrally located with respect to said chamber, said exit of said passage being radially disposed from said entrance in said valving surface in a region contacted by said Kingsbury pads and slots and said exit having a width less than the width of said slot, said Kingsbury pads normally blocking said exit and movable relative to said exit so as to momentarily open said exit to each slot to provide limited communication between said chamber and a low pressure region disassociated with said low pressure port for decompressing said chamber while said chamber is out of communication with said high and low pressure ports.

2. The combination, as defined in claim 1, wherein said barrier has a width substantially equal to twice the width of said slot plus the width of said chamber, whereby the width of said barrier is minimal.

References Cited UNITED STATES PATENTS 3,199,461 8/1965 Wolf 103-62 3,238,888 3/1966 Budry et a1. 103-62 2,155,455 4/1939 Thoma 103-62 2,298,850 10/1942 Vickers 103-62 3,092,035 6/1963 Freeman 103-62 3,094,078 6/1963 Brueder 103-62 3,249,061 5/1966 Ricketts 103-62 3,362,342 l/l968 Flint et al. 103-62 FOREIGN PATENTS 684,551 12/1952 Great Britain.

WILLIAM L. FREEH, @Primary Examiner 

